Muffler



P. G. PEIK Nov. 3, 1936.

MUFFLER Filed Oct. 31, 1932 L7 La G- PUK Mmm, 7L mw@ www:

Patented Nov. 3, 1936 PATENT OFFICE MUFFLER raul G. Peik, chicago, nl.,W. Taylor Company, W tion of Ohio assignor to The Halsey arren, Ohio, acorpora- Application October 31, 1932, Serial No. 640,558

1 Claim.

This invention relates to muillers for silencing the exhaust noises ofengines, particularly of .internal combustion engines. y

The generalobject of the invention is to provide a combined acoustic andresonator mulller, of exceptionally low production cost having adegreeof compactness heretofore unattained in muillers of comparableeiliciency.

Another object of the invention is to provide a durable eillcientcombined 'acoustic and resonator muiller of low construction cost whichembodies a series of resonator chambers of substantial length Whencompared with the length of the muffler.

Still anotherv object of the invention is to provide a combined acousticand resonator muffler of the type referred to above with a series ofresonator chambers tuned within narrow ranges with respect to each otherto broaden the range of frequencies in which the muffler will silencelow sound frequencies f Fundamentally all Asound deadening is due toresonance action. The highest eiiici'ency of sound deadening,that is,elimination of any sound wave in one cycle,-is attained only byproviding a separate chamber tuned exactly to the length of that wave.This method yis not feasible in a muiiier, due to the multiplicity ofsound waves in the exhaust stream, and the constant variation of theirfrequency due to the acceleration and de-celeration of the engine. Whileeach individual air space in sound absorbing material employed inmuilers of the so-called acoustic type, is far too small to have aneillcient sound deadeningl action in one cycle, acoustic mufllers arenevertheless very efficient in deadening high frequencies of sound dueto the multiplicity of air spaces and the high rate of oscillation ofthehigh frequencies. Thus, the so-called acoustic mufliers are extremelyeilicient in eliminating the high frequencies, but (for reasons whichare explalned later) are so inefiicient in their action on the lowfrequencies that such muiliers must be' made in a considerable length toobtain the necessary elimination of the low sound frequencies, so longin fact that it is common practiceto make them in two units so that theycan be mounted between the re-inforcing members of the modern automobilechassis.

'I'he following brief reference to a'coustic muffiers and resonatormuiiiers will serve to show how the above objects are attained and tobring out the main/features of the invention.

Resonator muiliers in 'turn are extremely efiicient in deadening lowfrequencies in an exhaust gas stream. Their efficiency is limited due tothe multiplicity of sound waves in the exhaust stream 4use is limited toautomobiles with relatively large frame structures.

The objects and advantages of the invention,

will become more apparent fromthe following description, when taken inconjunction with the accompanying drawing, wherein:

Figure l is a longitudinal sectional view of an exhaust mufer accordingto the invention, the section being taken on line I--l 'of Figure 2;

. Figure 2 is a transverse sectional View taken on line 2--2 of Figure1;

' Figures 3 and 4 are ytransverse sectional views taken on lines 3-3 and4-4 respectively of Figure 1; I

Figures 5 through 3 show a slightly modified form of the muliierprovided with separating fins to increase the number of resonatorchambers employed, thus, Figure 5 is a longitudinal sectional viewthrough the modified muffler taken on line 5 5 of Figure 6;

Figure 6 is a transverse sectional view taken on line 6-6 of Figure 5;

Figures 7 and 8 are transverse sectional views taken on lines 1--1 and 88 respectively of Figure 5.

Referring more particularly to the structure disclosed in Figures lthrough 4 of the drawing,

- the muffler I comprises a series of telescoped cylinders 2, 3 and 4arranged in spaced relationship with respect to each other. The outercylinder 2 and the adjoining cylinder 3l are connected at opposite endsin any suitable manner, as by welding to the front and rear end Walls 5and 6 respectively, thus forming resonator chamber 'l of ring shapedcross-section between these two cylinders. End wall 5 is formed with aninlet extension 8 having an outlet opening 9, and end wall 5 iscentrally perforated to form an opening I0.

'Ihe third cylinder 4 lis somewhat shorter and at its rear end welded torear end wall 6. The front end of cylinder 4 is welded to an inner wallI2 which in turn is secured to the inner wall of cylinder 3. Front endwall 5 is spaced a slight distance from inner wall I2 due to thedifference in length between .cylinders 3 and 4, thus forming a chamberIl at the front end of the muiller.

Cylinder 4 encloses a round sleeve or pipe IB in axial alignment withthe respective inlet and outlet openings 9 and I0, and extending frominlet opening I3 in inner wall I2 of shell 4 to and through opening I inrear end wall 8, thus forming a ring shaped chamber il within cylinder4. Pipe I5, which is made of perforated sheet metal, communicatesthrough its periorations with the interior of cylinder 4 surroundingsaid pipe. The ring shaped chamber Il in cylinder 4 is packed with anysound absorbing fire proof material i8 such as expanded mlcaceousmaterial, slag wool, steel wool etc. and communicates with the spaceinside of pipe I5, as previously described, which space constitutes anunobstructed main passage for the exhaust gas.

'I'he silencing efficiency of the structure Just described is moreeiective on the high sound Irequencies than on the lower ones, thelatter being more readily muilied or silenced by resonating action. Goodmuiiling on both high and low frequencies has heretofore only beenobtained by employing relatively long mufiiers, which as pointed outabove cannot be used on reinforced short frame structures ofautomobiles. In order to obtain a resonator effect in combination withthe acoustic action of the muiiier so far described without greatlyincreasing the length of the muier, the space between shells 2, 3 and 4is utilized as a resonator chamber I9. Chamber I9 which may be tuned tosilence the loudest period of the low sound frequencies of the exhaustgas stream, is approximately twice the length of the outer cylinder 2and consequently is about double the length o! the muiiler as a whole,one half of the length of chamber I9 constituting the outer ring shapedspace between cylinders 2 and 3, and the other half constituting theinner ring-shaped space between cylinders 3 and 4 which in effect servesas a second resonator chamber.

A series of openings or slots 20 in the wall. of cylinder 3 close to oneend thereof provide direct communication between the two halves ofchamber I9, and a series o! openings 2| in the wall of said cylinderclose to the opposite end thereof provide direct communication betweenchamber I4 and one end only of resonator chamber I9. Therefore as thechambers are connected in series the same will be caused to function asa compound resonator.

For internal combustion engines having an unusually complex combinationof distinct loud periods o1 low frequencies the number of resonatorchambers of the mufiier is preferably increased. Such a structure isdisclosed in Figures 5 to 8 of the drawing, wherein I show a mumerclosely resembling the structure shown in Figures i-4, with theexception that the space between shells 2 and l and shells 3 and 4 issubdivided by fins 22 and 23 respectively, whereby two elongatedreversed or U-shaped resonator chambers 24 and 25 o! substantial lengthare formed, which therefore function as a simple resonator. The lengthof chambers 24 and 25 may be individually adapted to silence the loudestperiods of the two lowest sound frequencies of the exhaust gas stream byarranging the communicating openings or slots 2D', 20" in cylinders 3and 4 more or less apart from the end of said cylinders, but slots 2lishould be so positioned that the chambers `24 and 25 will besubstantially longer than the length of the outer cylinder 2 andconsequently longer than the length of the muiiier as a whole. Thecommunicating passages 2| between the halves of chambers 24 and 25 arearranged similarly to openings 2l in the muffler previously described.

It will be understood that muiiiers according to the invention canreadily be built with any number of simple resonator chambers of therequired tuning either by providing further subdivisions by means ofadditional fins, or by increasing the number of shells or cylinders, andthat these muiiiers possess very high mufiiing efficiency despite thefact that the length of the muilier is comparatively short.

Having thus described my invention, what I claim is:

A muiiier for silencing the exhaust noise of internal combustionengines, comprising an unobstructed main passage having a plurality o!per- Icrations therein, an expansion chamber having sound absorbingmaterial packed therein and encircling said passage and communicatingtherewith through said perforations, and two substantially U-shapedresonator chambers, each being of substantially lgreater' length thansaid muiiier and each being in communication with the main passage, saidresonator chambers being spaced from the main passage by ditlerentradial distances.l

PAUL G. PEIK.

